Preparation and isolation of alkali metal and ammonium sulfonates of long chain carboxylic acids



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United States ice A ,;;;,f;,,

PREPARATION AND ISOLATION OF ALKALI METAL AND AMMONIUM SULFONATES 'OF LONG CHAIN CARBOXYLIC ACIDS No Drawing. Filed Apr. 26, 1956, Ser. No. 580,728

6 Claims. (Cl. 260-400) The present invention relates to the preparation of alkali metal and ammonium salts'of long' chain sulfocarboxylic acids and, particularly, to an improved method of neutralizing said acids and isolating the resulting salts. It is known that long chain canboxylic acids are con- I verted into a-sulfocarboxylic acids by means of sulfonating agents such as chlorosulfonic acid (U.S.P.' 2,360,968;

.U.S.P. 2,413,199) in the presence or absence of solvents or diluents (U.S.P. 2,448,370) and with or withoutcatalysts (U.S.P. 2,268,443). boxylic acids are isolated in the form of their salts and, to this end, it is conventional procedure to form the salts by neutralization of the reaction mixture with a strong alkali-such as sodium hydroxide or the like. Neutralization may be effected either before or after removal of the solvent or diluent or'by' pouring the sulfonation mixture onto the alkali.

The detergent properties of long chain sulfocarboxylic acids and their use in the preparation of detergents made it mandatory that changes be effected in the conventional neutralization process in order to realize the salts in a pure form and in a substantially dry condition. It was, therefore, recommended that crude mixtures of sulfonated long chain carboxylic acids be neutralized in vacuum (U.S.P. 2,613,218) or by means of anhydrous sodium sulfite in dry form or suspended in organic solvents and,

in this connection, reference may be made to U.S.P. 2,511,043 and 2,607,801. Other proposals were that neutralization of the sulfonated material be effected with solid sodium bicarbonate or lime (U.S.P. 2,511,043), potassium hydroxide in methanol (It. 433,792) or sodium acetate and sodium carbonate (JACS 75, 4859 (1953)). In any case, either alkali or the salts of weak acids were used for the neutralization of the crude mixture. Actually, sodium acetate or Na SO will presumably also give monosodium salts but alkali metal chlorides are much cheaper.

We have now discovered that the isolation of alkali metal and ammonium sulfonates of long chain sulfocarboxylic acids can be greatly improved while obtaining such salts in a substantially pure form and dry condition by neutralizing crude sulfonated long chain carboxylic acids in inert solvents with alkali metal or ammonium chlorides to selectively effect salt formation with the sulfo but not with the carboxy group.

It is an object of the invention to provide an improved method of isolating alkali metal and ammonium sulfonates of long chain carboxylic acids from crude sulfonation mixtures by means of alkali metal and ammonium chlorides.

It is a further object of the present invention to effect such neutralization with saturated aqueous solutions of alkali metal and ammonium chlorides.

It is a further object of the present invention to isolate the alkali metal and ammonium sulfonates in a substantially pure condition and dry form.

The carboxylic acids contemplated for sulfonation herein may be typified by the following general formula:

Usually, the free sulfocar-' alkali: metal chlorides or a ammonium .chlorides but R- -C;OOH in which' R is an aliphatic chain of at lease 6 ca rbon atoms such as hexyl, heptyl, octyl, nonyl, decyl, dodecyhj tetradecyl, heptadecyl and the like. Acids which are. especially suitable are those which are commonly used in detergent manufacture such as myristic acid,,palmitic acid and the like. I Y

The sulfocarboxylic acids neutralized accordingtoour procedure are formed according to conventional sulfonation processes involving the use of a sulfonating agent such as sulfur trioxide orchlorosulfonic acid in an inert.- diluent or solvent such as carbon tetrachloride or the like. Any method of sulfonation used in the prior art may be employed to produce the crude mixtures subsequently. neutralized and isolated; by us in the'form of the desired, sulfonates. -The reaction between the crude sulfonation mixture? and the alkali metal or ammonium chloride is preferably: effected by adding'a saturated aqueous solution of: theselected chloride to the 'hot SUllfOl'lfltlOIl mixturewhile stirring; After the reaction has subsided, a suitablet organic solvent such as acetone, methylethylketone'oru any other inert organic solvent which is misciblefwitht j water may be added to -expedite the filtration'of the sulfonates which have been formed. The quantity of alkali metal or ammonium chloride used is about equivalent: to the amount of sulfurtrioxide or 'itsequivalent usedfor' sulfonation." I 5 3 The chlorides which are employed rnayib': any ofthefi e prefer to use sodium, potassium or ammonium chloride ii Each of these operates smoothly to effect the desired con-- version of the sulfocarboxylic acids to the corresponding alkali metal or ammonium sulfonates with formation of HCl.

A peculiar feature of our procedure resides in the factv that the alkali metal or ammonium chloride, while forming a salt with the sulfo group, is indifferent to and does: not react wit-h the carboxy group. As a conseque'nce,. the salt formation which the sulfocarboxylic acid under-- goes is selective in that it involves only the sulfo group.. This greatly expedites the isolation of the sulfonates in a;

substantially pure form and dry condition.

It is known from the literature that the conventional? i monosulfonation of long chain fatty acids results in the introduction of the sulfo group on the a-carbon atom, i.e.",. that attached to the carboxy group. Inasmuch as only the sulfo group is converted to a salt group when satu-- rated fatty acids are treated according to our procedure; the compounds obtained will have the following structural 750 mls. of carbon tetrachloride and 284 grams of stearic acid were heated to boiling. Without heating, 70 mls. of freshly distilled chlorosulfonic acid were added, with stirring, within 10 minutes. After refluxing for another minutes, the evolution of HCl subsided.

To the hot sulfonation mixture were added 62 grams of a saturated aqueous solution of sodium chloride, within five minutes, without heating. After stirring for another 10 minutes, 3.7 liters of acetone were added, the mixture cooled, filtered and washed again with acetone. A brownish-white, well-crystallized product is formed which is; pure enough for most purposes. purified by suspending with stirringin 2.5 liters of acetone, filtering, washing, and warming the filter cake to 90 in four liters of 6 N acetic acid over a period of 30 minutes. After cooling, filtering, washing, and drying, a white light powder is formed. Yield: 200 grams;,M.P. 292-293. (dccomp). Analysis: S found 7.73%, theoretical 8.3%; acid no. found 137, calc. 145.1.

Example II A 2-liter round bottom three-necked flask equipped with a dropping funnel with attached CaCl tube, a stirrer and reflux eondenserwith an attached CaCl tube (the reflux condenser being attached to a Barrett receiver) was charged with 228.3 grams (1.0 mol) of myristic acid and 400 mls. of dry carbon tetrachloride.

To the warm, but not refluxing, stirrred mixture were added, dropwise, over a period of 20 minutes, 72 mls. (1.1 mols) of chlorosulfonic acid. The mixture was refiuxed with stirring for an additional four hours. The reaction mixture was poured into a 2-liter beaker, and 200mls. of a saturated salt solution were added in a thin stream while the mixture was stirred quite rapidly. The mixture was cooled, filtered and the filter cake suspended in 500 mls. of acetone. The mixture was again filtered, sucked dry and the filter cake recrystallized from 2 liters of water. The precipitate was filtered otf, washed with 200 mls. of acetone and air dried. The yield was 175 grams and the product melted above 300 C.

Example 111 e The procedure was the same as in Example 11 except that the acid employed was palmitic and the chloride was ammonium chloride.

Modifications of the invention will occur to persons skilled in the an and we, therefore, do not intend to be It can further be am-1,152 r a .4 limited in the patent granted except as necessitated by the appended claims.

We claim:

1. In the process of producing u-SlllfOCfil'bOXYliC acids by treating with a sulfonating agent, a carboxylic acid of the formula:

in which R is an alkyl group of at least 6 carbon atoms, the improvement which comprises isolating the resulting sulfocarboxylic acid as a sulfonate selected from the class consisting of alkali metal and ammonium sulfonates by adding to the crude reaction mixture an aqueous solution of a'salt selected from the class consisting of alkali metal and ammonium chloride and isolating the resulting solid product.

2. The process as defined in claim 1, in which the chloride is added in the form of a saturated aqueous solution.

3. The process as defined in claim 1, in which the chloride is added in the form of an aqueous saturated solution and the chloride is used in an amount substantially equivalent to the amount of sulfonating agent.

4. The process as defined in claim 1, wherein the acid is stearic and the chloride is sodium chloride.

5. The process as defined in claim 1, wherein the acid is myristic acid and the salt is sodium chloride.

6. The process as defined in claim 1, wherein the acid is docosanoic acid and the salt is sodium chloride.

OTHER REFERENCES Weil: J. Am. Chem. Soc. 75, 2526-2527 (1953). 

1. IN THE PROCESS OF PRODUCING A-SULFOCARBOXYLIC ACIDS BY TREATING WITH A SULFONATING AGENT, A CARBOXYLIC ACID OF THE FORMULA: 